38 HAWAIIAN AND OTHER PACIFIC ECHIXI. 



In a specimen measuring 15 mm. in diameter and 9 mm. in height there 

 are four and five interambulacral plates. The abactinal system measures 

 9 mm. across, the actinal system 8 mm. The median ambulacral zone con- 

 sists of two vertical rows of secondary tubercles about equal in size to those 

 surrounding the scrobicular area. In the younger specimens of Milkri 

 and frar/ilis the genital pores are frequently not developed (PI. 23, fig. 5), 

 and the actinal interambulacral plates are limited to a very small area 

 between the ambulacral plates (PI. 23, fig. 6). 



Neither tridentate nor large globiferous pedicellarias are to be found. 

 The small globiferous ones occur every where, but are not specially abundant. 

 They are very variable, but the valves are somewhat more slender than in 

 MiUeri; the lip is generally present, but the end-tooth is usually wanting. 

 The valves range in length from .40 to 1.00 mm., and the stalk is about 

 equal to them, or may be as much as twice as long. 



Station No. 3783. Off Kamchatka j S. E. Cape, Copper Id. 1567 fathoms. 

 Gy. V. s. gn. m. 



AcANTnociDARis Mort. 



It is not surprising that Mortensen^ should have established this genus 

 without any further examination than the superficial one he was able to 

 make of the specimens in the British Museum and in the Jardin des Plantes 

 and of the pedicellarii\3 he figured of Cidaris curvatkpinis Bell." For this 

 cidarid is indeed a most striking Echinoid and is remarkable for its 

 huge curved })rimary spines resembling those of Coelopleurus, though they 

 are not smooth, and end in a shallow grooved socket and not in a point as 

 in ihal genus. The base of the primary spines above the milled ring 

 is smooth, with fine striation, and indistinct, undulating ribs or ridges 

 extend to the base of the shoe, which is sharply fiuted or longitudinally 

 ril)l)od. Tlie primaries are curved near the extremity and are also often 

 llattcned there. The shaft of the spine is not more than one third the 

 length of the shoe. The longest radiolos are on the abactinal interambu- 

 lacral plates (Pis. ;^)7, 38). The radiolos of the actinal part of the test 

 (Pl.s. 12''. figs. IS, 19 : 37; 39, fig. /) are much flattened, slightly dished, 

 anil have the sliaft tipped with a ronsjiicuous. short, curved shoe or cap, as 

 in Slojdianocidaris. The larger prinuM-y spines are somewhat triangular in 

 section, the curved abactinal side of the radiole being wider than the side 



' IngoK ExjHjd. Eohinoiile.'i I. p. 21. 



• Trails. Zool. Soc. Undon, XIII. 1«>.1. p. 30-3. PI. XXXVIII. 



